Author Topic: Snapped bolt, now what?  (Read 2409 times)

Offline Athame57

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Snapped bolt, now what?
« on: July 01, 2025, 11:37:33 AM »
While undoing the bolts holding my front fender to the stanchion things got very stiff with the last bolt and....snap.  ::) See it in the right hole in the image? It isn't even a standard arrangment, I had prchased new bolts for this but found someone down the line has drilled through, made a thread and sunk bolts that have a nut on the other side.
As you can see the two ends of the snapped bolt are within the the hole itself.
I can't do this on my own that's for sure, but I'll have to wait until friday now to go to the garage (pension day)  ;)
MMMM....I hope they can fix this, what might I be in for? :-\
I brake for animals!
1978 CB400F2 called Elen.

Offline Skoti

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Re: Snapped bolt, now what?
« Reply #1 on: July 01, 2025, 12:31:10 PM »
Probably needs to be drilled out.
Properly secured using a pillar drill and vice.

Correct alignment is essential to prevent the drill bit going off centre.

Maybe an M6 thread insert such as helicoil could then be fitted. 


Or if you're lucky and it's possible to hold the broken stud with vice grips, then apply a wee bit heat and it might just come out.


Better to remove the fork slider and take it to your chosen repair shop or engineer friend.


Good luck

Skoti 
Skoti


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1976 Honda CB750F1

Offline Bryanj

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Re: Snapped bolt, now what?
« Reply #2 on: July 01, 2025, 02:09:38 PM »
It will have to be drilled out, probably too far gone for helicoil but i bought some inserts from ebay 6mm inside 8mm outside

Offline Athame57

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Re: Snapped bolt, now what?
« Reply #3 on: July 01, 2025, 02:29:45 PM »


Or if you're lucky and it's possible to hold the broken stud with vice grips, then apply a wee bit heat and it might just come out.
Alas, there is no stud to get to grips with!  ::)
I brake for animals!
1978 CB400F2 called Elen.

Offline exvalvesetdabbler

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Re: Snapped bolt, now what?
« Reply #4 on: July 01, 2025, 02:55:49 PM »
A few heat cycles with penetrating fluid in between and then drill it  the right size for a stud extractor. You might get lucky and it spins out when the drill bit bites.

If someone put it in with red locktite the heat should break it's grip.

If it can be drilled m6 then a helicoil should work.

Have used these at work on many occasions
https://voelkel.com/en/thread-repair-kits-6-x-1-0-1-5d/04073

Regards
Dave

Offline ST1100

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Re: Snapped bolt, now what?
« Reply #5 on: July 01, 2025, 03:31:56 PM »
Correct alignment is essential to prevent the drill bit going off centre.
I usually use a punch to center the thin (2.5~3mm) pre-drilling... and apply a drop of drill/cut-coolant in the tip...
And I've gotten me a set of LHS drill-bits; works flawless, most of the time the heat and torque alone drive the stub out.
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'00 ST1100Y, '04 ST1100R, '07 NT700VA, CB500K2, CB500K1...

Offline Athame57

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Re: Snapped bolt, now what?
« Reply #6 on: July 01, 2025, 03:33:39 PM »

If someone put it in with red locktite the heat should break it's grip.
Definatley no red loctite there, most of the long bolt had already come out. Thanks for the link Dave.
I brake for animals!
1978 CB400F2 called Elen.

Offline Johnwebley

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Re: Snapped bolt, now what?
« Reply #7 on: July 01, 2025, 03:51:33 PM »
Is any of the stud projecting??

I have seen them built up using electric welding,

With the heat cycles and penetrating fluid it should come out

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Offline Athame57

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Re: Snapped bolt, now what?
« Reply #8 on: July 01, 2025, 04:48:33 PM »
Is any of the stud projecting??

No, nothing sticking out to get a hold of .  :(
I brake for animals!
1978 CB400F2 called Elen.

Online McCabe-Thiele (Ted)

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Re: Snapped bolt, now what?
« Reply #9 on: July 01, 2025, 05:58:09 PM »
I had stripped threads on both my 500 forks where the top brake bracket fits plus a missaligned helicoil.
I took the bottom part of the forks to a local engineering firm, they fitted something they called a Slug or a Pig?
I had about 5 or 6 threads Helicoiled as well, it cost me £170 in total.
Honda CB400NA Superdream (current money puddle)
Honda CB500 K1 (second money pit)
https://www.sohc.co.uk/index.php/topic,28541.0.html
Honda CB400 four super sport (first money pit)
Link to my full restoration http://www.sohc.co.uk/index.php/topic,23291.0.html
This is a neat 500 restoration in the USA.
http://forums.sohc4.net/index.php/topic,151576.msg1731556.html#msg1731556

Offline taysidedragon

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Re: Snapped bolt, now what?
« Reply #10 on: July 01, 2025, 06:08:46 PM »
If the screw went right through to fit a nut on the inside of the leg, I bet there was some corrosion on the thread which was sticking out. That's probably why it got stiff then snapped when the corroded part was inside the threaded hole.
If so it might come out easier if you try and remove it from the inner side of the slider. Reversing back out.
Gareth

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1965 T100SS

Offline exvalvesetdabbler

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Re: Snapped bolt, now what?
« Reply #11 on: July 01, 2025, 07:40:32 PM »
My thoughts as well.  Drill from the opposite side to where the bolt head was.  Did the bit that came away with the bolt head have threads. Ie a set screw or a plain shank.  Beginning to wonder if someone just hammered a bolt into what was left of striped threads in which case it might press out after applying heat.

Offline andy120t

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Re: Snapped bolt, now what?
« Reply #12 on: July 01, 2025, 07:41:06 PM »
Depending on the outcome it might be more cost effective to find a used replacement.
andy120t

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Offline Athame57

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Re: Snapped bolt, now what?
« Reply #13 on: July 01, 2025, 10:44:04 PM »
Depending on the outcome it might be more cost effective to find a used replacement.
Thought of that. I found a good one on 400four site, just in case I need that contingency plan.  ;)
I brake for animals!
1978 CB400F2 called Elen.

Offline Murf

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Re: Snapped bolt, now what?
« Reply #14 on: July 02, 2025, 11:03:16 AM »
As said Probably a real bodge with a bolt of some odd thread just forced in. But easy fix for a competent engineer. 

Get old bolt out as described earlier in this thread, then if resulting hole is too big for a thread insert,  drill to nice clean hole, make up a stainless steel bush with internal m6 thread that is an interference fit in hole,  put bush in freezer for 1/2 hour, heat area around hole, press cold bush into hole, use some locktight if desired, let it all cool and you now have a nice repair that can’t be seen.

 

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